The importer should retry on some of the frequent errors, see the following:
MariaDB [s54509__wiki_importer]> select error_message from page where imported_successfully=0\G
*************************** 1. row ***************************
error_message: {"error": {"code": "missingparam", "info": "The \"token\" parameter must be set.", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1408"}
*************************** 2. row ***************************
error_message: {"error": {"code": "mwoauth-invalid-authorization", "info": "The authorization headers in your request are not valid: Nonce already used: 179037234151031446781614209411", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1341"}
*************************** 3. row ***************************
error_message: {"error": {"code": "missingparam", "info": "The \"token\" parameter must be set.", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1363"}
*************************** 4. row ***************************
error_message: {"error": {"code": "missingparam", "info": "The \"token\" parameter must be set.", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1286"}
*************************** 5. row ***************************
error_message: {"error": {"code": "missingparam", "info": "The \"token\" parameter must be set.", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1343"}
*************************** 6. row ***************************
error_message: {"error": {"code": "mwoauth-invalid-authorization", "info": "The authorization headers in your request are not valid: Nonce already used: 9586967659476934241614210427", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1285"}
*************************** 7. row ***************************
error_message: {"error": {"code": "mwoauth-invalid-authorization", "info": "The authorization headers in your request are not valid: Nonce already used: 102686593206814731021614210492", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1410"}
*************************** 8. row ***************************
error_message: {"error": {"code": "mwoauth-invalid-authorization", "info": "The authorization headers in your request are not valid: Nonce already used: 116860847700323664141614211278", "*": "See https://mni.wikipedia.org/w/api.php for API usage. Subscribe to the mediawiki-api-announce mailing list at <https://lists.wikimedia.org/mailman/listinfo/mediawiki-api-announce> for notice of API deprecations and breaking changes."}, "servedby": "mw1283"}
8 rows in set (0.02 sec)Those errors sound like a temporary one, and the right reply is to just try it once more.